Eggs are a popular and nutritious food product. Their appealing flavor and texture have caused them to be prepared and consumed in numerous ways, particularly as a breakfast food. Traditionally, eggs have been prepared as a separate dish, or as part of a dish such as omelets, quiches, sandwiches, and recently in breakfast burritos.
As time becomes more and more valuable to the consumers of food products, and the demand for nutritious, quick and easy to prepare foods has grown, producers have sought to provide prepared food products that contain eggs. Because of the difficulty in storing and preserving fresh eggs, these products have often been stored in the freezer, to prevent the growth of undesirable microorganisms in the egg product.
Although freezer storage can be an effective method of storing egg products without growth of microorganisms, the method has given rise to other challenges in the production of egg-containing food products. Because a whole egg is made up of about 70% water by weight, when a prepared egg product is frozen ice crystals are formed. When these crystals melt the water is not completely reabsorbed into the egg product, and some of the water "weeps" out of the eggs. If the eggs are prepared separately, this results in the thawed eggs sitting in a puddle of water and may also result in the eggs having a rubbery texture. If the eggs are prepared as part of the filling of a food that has a crust or pastry component, this results in the transfer of water to the crust or pastry and a soggy texture. Further, the high levels of free water in most egg containing products result in relatively slow reheating times when the product is exposed to radiant heat, such as in a toaster. This is especially problematic when the egg product is used as part of a filling.
In the past, this problem had been addressed by the use of powdered eggs that are reconstituted when combined with additional ingredients. This system allowed the free water in the egg product to be easily controlled, but still resulted in the product having undesirable textural characteristics. The reconstituted egg product has a tendency to become tough or rubbery when it is frozen for storage and then thawed for consumption. This tough texture is believed to be caused by a loss of water when the egg protein is denatured in the dehydration process.
The prior art has attempted to overcome these problems in a number of different ways. Rapp et al., in U.S. Pat. No. 4,469,708, describe a freeze-thaw stable egg product and a process for preparing the product. The product comprises loosely cohered pieces of cooked egg in a batter coating. The egg mixture contains water binding carbohydrates such as a cold-water-insoluble starch and a hydrophilic colloid. The moisture content of the egg mixture is about 72 to about 80%.
In U.S. Pat. No. 3,640,731, Kaplow et al. disclose a shelf stable egg product wherein dried egg white, whole egg solids or egg yolks are blended with 20-40 wt-% of a polyhydric alcohol. This mixture is then combined with starch hydrolyzate solids and an antimycotic to form a shelf stable egg product having a moisture range of 14-32% and an A.sub.w of between 0.65 and 0.80.
Kahn et al., U.S. Pat. No. 4,244,976 disclose an intermediate moisture content frozen egg yolk composition containing egg yolk, sugar, water and a stabilizer. In order to maintain the bacteriostatic effect of the mixture, the sugar to water ratio is at least about 1:1.
Each of the prior art methods of preparing a freezable egg product have certain undesirable features. For example, if large amounts of glycerol are used, the bittersweet taste of glycerol becomes very pronounced and it becomes necessary to mask the taste of glycerol. If large amounts of sugar are used, unless the product is a dessert product, it is necessary to reduce the flavor impact of the sweetness component, for example, by incorporating a bitterness principle such as quinine and caffeine.
Clearly, a substantial need exists for an egg based product that is suitable for freezing which does not become rubbery or tough during storage and may be quickly reheated.